1. Field of the invention
The present invention relates to a smelting reduction apparatus and a method for producing molten pig iron using the apparatus, in which the molten pig iron is produced by using raw iron ore, sintered ore or iron pellets. More specifically, the present invention relates to a smelting reduction apparatus and a method for producing molten pig iron using ths smelting reduction apparatus, in which the reduced iron is efficiently discharged from a pre-reducing furnace to a melter-gasifier.
2. Description of the prior art
A typical prior art method is disclosed in U.S. Pat. No. 4,978,387 in which molten pig iron is produced without pre-treating iron ore and coal.
In the method of U.S. Pat. No. 4,978,387, raw iron ore and non-coking coal are directly used. Therefore, compared with other iron making processes, the pre-treating processes such as sintering and coking are skipped, with the result that the process and the facility are simplified.
As shown in FIG. 1, the melting-reducing apparatus of the above mentioned patent includes: a melter-gasifier 11 for gasifying the coal, and for melting the iron ore; a pre-reducing furnace 12 for indirectly reducing the iron ore by utilizing the reducing gas; and other auxiliary facilities.
As shown in FIG. 1, the prior art melting-reducing apparatus operates in the following manner. The iron ore is pre-reduced in the pre-reducing furnace 12 by utilizing the discharge gas which is produced within the melter-gasifier 11. Then the pre-reduced iron ore is melted and reduced at the melter-gasifier 11. The gas which is discharged from the melter-gasifier 11 is supplied through an ascending duct 13 and a cyclone 14 to the pre-reducing furnace 12. The fine iron ore which is collected by the cyclone 14 is spouted through a recycling device 15 and a melter-burner 16 into the melter-gasifier 11. A part of the discharge gas which has passed through cyclone 14 is supplied through a venturi scrubber 17, a compressor 18 and a compressed gas circulating duct 19 into the ascending duct 13.
The melter-gasifier 11 gasifies the coal so as to produce a reducing gas which is needed for an indirect reducing of the iron ore. Further, by utilizing the heat generated in this process, the iron which has been indirectly reduced at the pre-reducing furnace 12 is melted. Meanwhile, the pre-reducing furnace 12 indirectly reduces the raw iron ore by utilizing the reducing gas which is produced at the melter-gasifier. As shown in FIG. 2, six reduced iron discharge tubes, each of which has a discharge screw 111 are installed in a radiative form. Therefore, the discharge screws 111 are made to revolve, so that the reduced iron can be continuously discharged, and that the discharged iron can be injected into the melter-gasifier through the top of it.
However, in the above described reduced iron discharge method, if any one of the discharge screws becomes abnormal, or if a discharge difference occurs due to mechanical or operational cause, then the iron which is injected into the reducing furnace produces an imbalance.
If an imbalance occurs, the flow of the reducing gas is biased. Consequently, the iron ore reducing efficiency is drastically lowered, and unreduced iron ore is charged into the melter-gasifier, with the result that an abnormality occurs in the control of the temperature of the melter-gasifier.